title: Postprandial glucose fluxes and insulin sensitivity during exercise: a study in healthy individuals.
abstract: Quantifying the effect size of acute exercise on insulin sensitivity (SI(exercise)) and simultaneous measurement of glucose disappearance (R(d)), endogenous glucose production (EGP), and meal glucose appearance in the postprandial state has not been developed in humans. To do so, we studied 12 healthy subjects [5 men, age 37.1 ± 3.1 yr, body mass index 24.1 ± 1.1 kg/m², fat-free mass (FFM) 50.9 ± 3.9 kg] during moderate exercise at 50% V(O₂max) for 75 min, 120-195 min after a triple-tracer mixed meal consumed at time 0. Tracer infusion rates were adjusted to achieve constant tracer-to-tracee ratio and minimize non-steady-state errors. Glucose turnover was estimated by accounting for the nonstationary kinetics introduced by exercise. Insulin sensitivity index was calculated in each subject both in the absence [time (t) = 0-120 min, SI(rest)] and presence (t = 0-360 min, SI(exercise)) of physical activity. EGP at t = 0 min (13.4 ± 1.1 μM·kg FFM⁻¹·min⁻¹) fell at t = 120 min (2.4 ± 0.4 μM·kg FFM⁻¹·min⁻¹) and then rapidly rose almost eightfold at t = 180 min (18.2 ± 2.6 μM·kg FFM⁻¹·min⁻¹) before gradually falling at t = 360 min (10.6 ± 0.9 μM·kg FFM⁻¹·min⁻¹). R(d) rapidly peaked at t = 120 min at the start of exercise (89.5 ± 11.6 μM·kg FFM⁻¹·min⁻¹) and then gradually declined at t = 195 min (26.4 ± 3.3 μM·kg FFM⁻¹·min⁻¹) before returning to baseline at t = 360 min. SI(exercise) was significantly higher than SI(rest) (21.6 ± 3.7 vs. 12.5 ± 2.0 10⁻⁴ dl·kg⁻¹·min⁻¹ per μU/ml, P < 0.0005). Glucose turnover was estimated for the first time during exercise with the triple-tracer technique. Our results, applying state-of-the-art techniques, show that moderate exercise almost doubles postprandial insulin sensitivity index in healthy subjects.
authors.affiliation: Department of Health Sciences Research, Mayo College of Medicine, Rochester, Minnesota;
authors.forename: Michele
authors.initials: M
authors.lastname: Schiavon
authors.forename: Ling
authors.initials: L
authors.lastname: Hinshaw
authors.forename: Ashwini
authors.initials: A
authors.lastname: Mallad
authors.forename: Chiara
authors.initials: C
authors.lastname: Dalla Man
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sparacino
authors.forename: Matthew
authors.initials: M
authors.lastname: Johnson
authors.forename: Rickey
authors.initials: R
authors.lastname: Carter
authors.forename: Rita
authors.initials: R
authors.lastname: Basu
authors.forename: Yogish
authors.initials: Y
authors.lastname: Kudva
authors.forename: Claudio
authors.initials: C
authors.lastname: Cobelli
authors.forename: Ananda
authors.initials: A
authors.lastname: Basu
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000465:Algorithms; D001786:Blood Glucose / Q000032:analysis*; D002096:C-Peptide / Q000097:blood*; D002250:Carbon Radioisotopes; D003903:Deuterium; D005240:Feasibility Studies; D005260:Female; D005934:Glucagon / Q000097:blood*; D005943:Gluconeogenesis; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism; D006801:Humans; D007262:Infusions, Intravenous; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009043:Motor Activity; D019518:Postprandial Period; D014316:Tritium; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D002250:Carbon Radioisotopes; D007328:Insulin; D014316:Tritium; D005934:Glucagon; D003903:Deuterium; D005947:Glucose
keywords: exercise; insulin sensitivity; oral minimal model